The present invention generally relates to the field of large area lighting, such as lighting for sports events. More specifically, the present invention relates to the response of lighting systems to power outages which could occur at sports events or other public gatherings.
Lighting Needs for Sports Venues
Sports venues and other large areas requiring lighting usually require varying levels of lighting for use at different times. The most light is required during active use of the facility for sports or activities. Less light may be required before the event when people are arriving and after the event when people are still present. A much lower level of light is required for emergency exit during power outages, and possibly for maintenance and security purposes when the venue is not occupied by large numbers of people.
The above three types of lighting that might be used at sports venues will be considered herein under the following definitions: “Event lighting” is lighting provided primarily on and near the sports field, track, etc. for the benefit of the participants, to allow the spectators to see clearly, for television lighting, etc. “Utility lighting” is lighting that is provided for spectators to be able to see and move about within the location, exit the stands, etc. It may be provided in part by “event lighting” and may be provided in part by separate fixtures or lighting systems. “Emergency lighting” is any lights or system of lighting that provides a minimum level of lighting to the location to allow safe exit of the location, or which may be useful for maintenance, security, or continued emergency use.
Adequate “event lighting” for participants in sports events is necessary to allow safe and effective conduct of a sport or activity. For instance, it is well known that the ability to perceive moving objects is related to several factors, including velocity, size, contrast, and color. If an object is moving very fast, is relatively small, is of low contrast with its surroundings or is a color similar to its background, it can be difficult to perceive. Because of this, sports such as baseball and automobile racing rely on a high level of event lighting to provide adequate lighting. Other sports or activities can also require a high level of event lighting.
“Utility lighting” for spectator safety and convenience is related to event lighting. A relatively low level of utility lighting in comparison to the required event lighting can be (by itself) adequate, since movement within the facility does not require the same degree of visual acuity, particularly since spectators do not normally have direct interaction with high speed activities such as throwing, batting, competitive driving, etc. However, when high levels of event lighting are present, the eye can be accustomed to the relatively high level of utility lighting. If the event lighting level is suddenly and dramatically reduced, spectators will be left without the ability of move easily within the facility until their eyes readjust to the diminished light level, and will typically experience some degree of unease with their surroundings due to the sudden and drastic change.
“Emergency lighting” for a typical sports venue is typically considered to be sufficient lighting to proceed safely to exits but is not considered adequate as utility lighting. Public facilities which use artificial lighting are normally required to provide emergency light at an illumination level and for a duration which is adequate for evacuation of the facility. A typical required duration is 90 minutes. However, the safe evacuation of a facility is not the only foreseeable use of emergency backup lighting. In the event of various types of disruptions or disasters, a venue such as a sports stadium might be used for emergency shelter, storage, emergency operations staging, etc. Thus the ability to provide extended lighting, even at a very low level, could be beneficial.
For sports venues, in the event of a power interruption, “required” emergency lighting may not be satisfactory or ideal, since emergency lighting levels do not provide adequate event or utility lighting. Many sports venues could benefit from having a system that provides substantially the same light level in the event of a power failure to help reduce the risk of low visibility of high-speed objects, or for aesthetic, convenience, or other reasons. For example, baseballs can be thrown or batted at a very high velocity—on the order of 100 feet per second or more. Loss of light, even for a very short time, would make it difficult to follow the movement of a ball in the air, which could result in a player or spectator being hit by the ball. Similarly, race cars travel at a very high rate of speed. If lighting were to be interrupted or be significantly diminished during an automobile race, drivers could lose control of their vehicles.
Types of Backup Systems
There are various existing types of backup systems. The Uninterruptible Power Supply (UPS) type of backup system (sometimes known as a “double conversion” or “online” system) provides instant full power to a lighting system in the event of a power interruption. It takes AC grid power and converts it to DC power. The DC power is used to charge storage batteries. The same DC power is fed to an inverter which converts DC to AC power to power a lighting system. In the even of power interruption, DC power from the storage batteries flows without interruption to the DC-to-AC inverter, which is able to maintain full AC voltage output to the lighting system without any loss of voltage or interruption or modification of the AC sine wave output. Considerations for use of this type of system include the fact that by itself, it maintains the same event lighting for a specified period, typically 90 minutes. This may completely exhaust the batteries, making it impossible to provide any extended lighting period. Since the very high levels of event lighting are only needed for a short time in order to complete potentially risky activities, this may not be an efficient use of limited backup power. Reducing lighting levels in order to increase duration of emergency lighting would require additional controls or manual switching of lights by knowledgeable personnel. Or, multiple backup systems would be required to provide power to different lighting systems having different output levels. No provision for adjustment of light levels is provided with a typical UPS type system. A complete backup system using a UPS type system may therefore be too expensive or complicated, or may not provide sufficient duration of backup, extreme low level lighting, or other desired benefits.
An “emergency light” type backup system typically provides low level illumination at a minimum level and duration required for evacuation of a venue. The lighting fixtures are provided for walking paths and exits, and do not provide the ability to complete or safely stop potentially risky sports activities.
Variations or combinations of these systems may be installed, which increases the cost and complexity of the backup system. A UPS system could be installed which allows event lighting to be continued for a given duration, while an emergency system provides extended lighting at a lower level. Still, gradual dimming would be difficult or impossible without extensive additional equipment and cost.
Desired Lighting Solutions for Sports Venues
It would therefore be desirable for sports venues, in the event of power interruption, to provide a high level of event and utility lighting, as well as emergency lighting that is at or above the minimum required level. It would be beneficial for these lighting levels to be provided for a longer duration and/or at a lower cost than is commonly obtained.
Specifically, there is a need for backup event lighting using existing lighting fixtures which in the event of a power failure provides uninterrupted event lighting that is of functionally identical intensity and quality to the primary lighting, for a duration sufficient to safely complete or terminate potentially risky activities. For a baseball game, this could allow the thrown or batted ball to be safely stopped, possibly for the play to be completed, helping to reduce the chance of players getting hit by an airborne baseball or a substantial disruption of the game or activity for a relatively short duration. Or for an automobile race, this would allow vehicles to slow down safely under a caution flag. Further, there is a need for the ability to provide a gradual transition from event lighting levels to lower levels, thereby allowing sufficient time for eye adjustment to lower lighting levels and reducing potential panic or discomfort which might arise due to sudden reduction in lighting levels.
Likewise, there is need for backup utility lighting, using existing event or utility lighting fixtures, that exceeds minimum standards for emergency lighting and that provides benefits in terms of duration and quality in comparison to existing standards for emergency lighting. This would lead to less inconvenience and less spectator discomfort or dissatisfaction. Further, there is a need for the ability to provide a gradual transition from utility lighting levels to lower emergency lighting levels, thereby allowing sufficient time for eye adjustment to lower lighting levels and reducing potential panic or discomfort which might arise due to sudden reduction in lighting levels.
Likewise, there is need for emergency lighting using existing event or utility lighting fixtures that exceeds minimum standards for emergency lighting and that provides benefits in terms of duration and quality in comparison to existing standards for emergency lighting. Further, there is a need for the ability to provide a gradual transition from emergency lighting levels to lower lighting levels which might still be useful in the event of extended power interruption, thereby allowing sufficient time for eye adjustment to even lower lighting levels and reducing potential panic or discomfort which might arise due to sudden reduction in lighting levels or complete loss of lighting. Thus the ability to provide lower light levels down to 10%, or even as small as on the order of 2% or less of original event or utility lighting levels could be beneficial and desirable.
Thus, improvements in the art are desirable.